JPH03138849A - Ion implanter - Google Patents

Abstract

PURPOSE:To keep the space charge effect of an ion beam nearly constant and suppress the fluctuation of the beam focus point position when operating parameters are changed by providing a gas guide port on a vacuum container constituting a beam transportation line, and guiding the gas into the beam transportation line through it. CONSTITUTION:A gas guide port 22 is provided on an ion source chamber 8, and gas can be guided into a beam transportation line from an ion source 2 to an analyzing electromagnet 12 through it. The ratio that ions in an ion beam 10 collide with gas molecules in the atmosphere to discharge electrons is increased, and the space charge effect is mitigated. The space charge effect in this segment can be kept nearly constant when operating parameters affecting the space charge effect such as the ion type, energy, and beam quantity (beam current) of the ion beam 10 are changed by adjusting the gas flow guided into the beam transportation line.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion implantation apparatus, and more particularly to means for suppressing fluctuations in the focal point position of an ion beam.

[Conventional technology]

FIG. 4 is a schematic diagram showing an example of a conventional ion implantation apparatus.

This ion implanter basically deflects an ion beam 10 extracted from an ion source 2 through an analysis electromagnet 12 having an analysis tube 14, and directs it to a predetermined beam focus point F in a target chamber 16 on the downstream side. The ion beam 10 is passed through an analysis slit 18 provided in the slit 18, thereby performing momentum analysis of the ion beam 10, selectively leading out an ion beam 10 consisting of ions of a desired mass, and making it incident on a target (for example, a wafer) 20. ing.

In this example, the ion source 2 has a structure in which an arc chamber 4 for plasma generation and an extraction electrode system 6 for extracting the ion beam 10 are housed in an ion source chamber 8 which is a vacuum container. is connected to the analysis tube 14 of the analysis electromagnet 12.

[Problem to be solved by the invention]

In the above-described ion implantation apparatus, the space charge effect in the ion beat 10 varies depending on the operating parameters such as the ion species, energy, and beam amount of the ion beam 10.

Therefore, for example, the divergence state of the ion beam 10 on the upstream side of the analysis electromagnet 10 changes, and the position of the beam focusing point F varies in various ways in the beam traveling direction. The broken line in FIG. 4 shows one example, in which the beam focus point F' is shifted downstream from the normal beam focus point F.

This results in reduced mass resolution, increased beam loss on the beam transport line (i.e. reduced beam transport efficiency),
Various problems arise in the basic performance of the ion implanter, such as changes in the beam shape on the target 20.

Therefore, the present invention has developed an ion implantation method that makes it possible to keep the space charge effect in the ion beam constant even when the operating parameters that affect the space charge effect as described above change, thereby suppressing fluctuations in the beam focal point position. The main purpose is to provide equipment.

[Means for Solving the Problems] In order to achieve the above object, the ion implantation apparatus of the present invention includes a gas introduction port provided in the vacuum container constituting the beam transport line from the ion source to the analysis electromagnet as described above, It is characterized in that gas can be introduced into the beam transport line from there.

[Effect]

When a gas is introduced into the beam transport line, the ions in the ion beam collide with gas molecules in the atmosphere and emit electrons at a higher rate, increasing the amount of electrons present in the ion beam and increasing the number of electrons in the ion beam. The neutralization rate is increased and space charge effects in the ion beam are alleviated. The degree can be adjusted by adjusting the flow rate of the introduced gas. As a result, even if operating parameters that affect the space charge effect, such as the ion species, energy, and beam amount of the ion beam, change, the space charge effect in the ion beam can be kept close to constant.

〔Example〕

FIG. 1 is a schematic diagram showing an ion implantation apparatus according to an embodiment of the present invention. The same reference numerals are given to the same or corresponding parts as in the example of FIG. 4, and the differences from the conventional example will be mainly explained below.

In this embodiment, the ion source chamber 8 as described above is provided with a gas introduction port 22 through which a gas 30 can be introduced into the beam transport line from the ion source 2 to the analysis electromagnet 12. ing.

Gas 30 is introduced, for example, from gas source 24 through pressure regulator 25, valve 26 and flow regulator 28.

The amount of gas 30 introduced into the ion source chamber 8 is specifically adjusted as described later, but the purpose is not to create a neutral particle beam but to introduce the ion beam 10 into the ion source chamber 8.
Since the purpose is to reduce the space charge effect of There was 10-”ror
(lower than r-order) is sufficient.

For the ion beam 10, the introduced gas 30 is an inert gas such as argon or neon, or the same gas as the source gas introduced into the ion source 2.
Furthermore, this is preferable from the viewpoint of preventing impurity ions from being mixed into the target 20.

When the gas 30 is introduced into the beam transport line from the ion source 2 to the analysis electromagnet 12 as described above, ions #
The rate at which ions in the ion beam 10 extracted from the ion beam 10 collide with gas molecules in the atmosphere and emit electrons increases, and the amount of electrons present in the ion beam 10 increases.
The neutralization rate of the ion beam 10 increases, and the ion beam l
Space charge effects in O are alleviated. The degree can be adjusted by adjusting the flow rate of the introduced gas.

Therefore, by adjusting the gas flow rate introduced into the beam transport line, the ion species of the ion beam 10,
Even if operating parameters that affect the space charge effect, such as energy and beam amount (beam current), change, the space charge effect in the ion beam IO within the above-mentioned section can be kept close to constant.

As a result, it is possible to suppress fluctuations in the position of the beam focal point F in the beam traveling direction, thereby preventing a decrease in mass resolution, a decrease in beam transport efficiency, a change in beam shape on the target 20, etc. This improves the characteristics of the ion implanter.

For example, when the ion species of the ion beam 10 is As'' or B'', the position of the beam focusing point F is, in the case of the conventional example, the beam Ti'1Jt of the ion beam 10 (beam i
t), the thickness changes as shown in FIG. 2 (in the figure, the top is the direction of movement toward the downstream side).

On the other hand, if the gas 30 is introduced into the ion source chamber 8 and the gas flow rate is changed according to the beam current of the ion beam 10 as shown in FIG. 3, for example, as in this embodiment, Since the space charge effect in the ion beam 10 approaches a constant value, the position of the beam focus point F can be kept constant even if the beam current changes.

By the way, in this embodiment, the gas 30 is introduced upstream of the analysis electromagnet 12 because:
Even if neutral particles with energy are generated due to the collision between zero and gas molecules, they can be removed by the analysis electromagnet 12, and as a result, neutral particles that are not measured by the beam current are injected into the target 20. It is possible to prevent errors in the dose amount from occurring. ■The divergence of the ion beam IO on the upstream side of the analysis electromagnet 12 has a relatively large effect on fluctuations in the position of the beam focus point, but the ion beam IO there This is because it is preferable in that it is possible to suppress the divergence of .

Note that the flow M of the gas 30 introduced into the ion source chamber 8 is adjusted depending on the ion species of the ion beam 10, the energy,
The relationship between the operating parameters such as the beam amount that affect the space charge effect and the gas flow rate required to keep the position of the beam focal point F constant with respect to the operating parameters (for example, as shown in Figs. 2 and 3). A curve as shown in the figure is created in advance as a database and stored in the control device 32, and the dose regulator 28 is automatically adjusted according to the operating parameters given to the control device 32. You can do it like this.

Also, unlike the above example, if there is another vacuum vessel such as a beam line tube connecting the ion source chamber 8 and the analysis tube 14 of the analysis electromagnet 12, the vacuum vessel may be Alternatively, a gas introduction boat 22 may be provided and the gas 30 may be introduced from there.

Moreover, in any case, a plurality of gas introduction boats 22 may be provided within the above-mentioned section.

〔Effect of the invention〕

As described above, according to the present invention, the neutralization rate of the ion beam can be adjusted by introducing gas into the beam transport line from the ion source to the analysis electromagnet. Even if operating parameters that affect the space charge effect, such as energy, beam amount, etc., change, the space charge effect in the ion beam can be kept close to constant.

As a result, it is possible to suppress fluctuations in the beam focal point position, thereby preventing a decrease in mass resolution, a decrease in beam transport efficiency, and a change in beam shape on the target, which is a characteristic of an ion implanter. will improve.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an ion implantation apparatus according to an embodiment of the present invention. FIG. 2 is a graph showing a schematic example of the relationship between beam current and beam focal point position. FIG. 3 is a graph showing a schematic example of the relationship between beam current and gas flow rate. FIG. 4 is a schematic diagram showing an example of a conventional ion implantation apparatus. 2... Ion source, 8... Ion source chamber lO.
...Ion beam, 12...Analysis electromagnet, 18...
Analysis slit, 20...target, 22...gas introduction boat, 30...gas, F, F'..., beam focusing point. Figure 2 Figure 2 Figure 2

Claims (1)

[Claims] (1) In an ion implanter configured to cause an ion beam extracted from an ion source to enter a target through an analysis electromagnet and an analysis slit provided on the downstream side thereof, a vacuum vessel forming a beam transport line from the ion source to the analysis electromagnet. An ion implantation apparatus characterized in that a gas introduction port is provided in the ion implanter, and a gas can be introduced into the beam transport line from the gas introduction port.